Fluid control devices



United States Patent [72] Inventor Victor James Chadwick Taplow, England [211 App]. No. 614,162 [22] Filed Feb. 6,1967 [45] Patented Dec. 15, 1970 [73] Assignee British Telecommunications Research Limited Taplow, England a British company [32] Priority Feb. 7, 1966, Mar. 16. 1966 [33] Great Britain [31 No. 5290/66 and 11,590/66 [54] FLUID CONTROL DEVICES 1 Claim, 5 Drawing Figs.

[51] int. Cl FlSc l/08 [50] Field of Search [56] References Cited UNITED STATES PATENTS 3,250,470 5/1966 Grubb 3,288,364 1l/1966 Vockroth,Jr.

3,350,008 10/1967 Avery 235/201pf 235/201pf 235/201pf Fluid Oscillator," A. E. Mitchell, 1.B.M. Technical Disclosure Bulletin, vol. 5, No. 6, Nov., 1962 p.25. (copy in Scien. Lib. & Gp. 360; 137- 81.5)

Primary Examiner- Samuel Scott Attorney- Young & Thompson ABSTRACT: In a bistable, wall attachment, fluid control device, control pressure is applied when the main fluid flow rate is below or marginally above the rate at which wall attachment first takes place. The level of the control pressure is such that it is not effective when the fluid flow rate is built up to a greater value.

The invention is used to provide a device having a latching lNHlBlT output and a latching AND output and to fluidic shift registers.

PATENTED 050151970 7 v 3547,13? sum 1 [IF 2 Amm rmw 6 f rC/Y U PATENTED UEEI 519m 3547-137 sum 2 OF 2 I fect the operation of valve or similar control members so as to produce switching operations similar to those-which can be produced in other circumstances by electrical circuits. Such fluid logic circuits can readily be made of small size and in many circumstances offer advantages over. corresponding electrical arrangements. y h

It has already been appreciated that it is possible to produce so-called pure fluid switches in which," owing to the phenomenon of wall attachment, fluid flowing in through an inlet port continues to follow one of two alternative paths each leading to an outlet port after it has been induced to take this path by a suitable fluid control signal at one of two control ports, movement to the other path being subsequently effected by a control signal at the other control port and the fluid then continuing to follow the other path after the control signal is removed. Such devices are hereinafterreferred to as wall attachment devices. The present invention is particularly concerned with such devices and its chief object is to permit them to be controlled by very' small pressures and flows.

The effect just mentioned is found to be dependent on the actual pressure of the main fluid stream, and at comparatively low pressures there is a state in which theflow is only just stable so that a very small control signal suffices to switch the fluid flow from one path to the other.

According to the invention a method .of controlling the flow of fluid in a wall attachment device comprises applying low pressure fluid control signals to the control ports thereof, the magnitude of'such control signals being so arranged that each can control the path through the device taken'by the fluid only if such control signal is applied when the rate of flow of fluid through the device is not greater than that atwhich wall attachment takes place and is maintained until such wall attachment has occurred.

The invention will be more readily understood from the foling drawings, in which:

FIG. I is a schematic sectional view of a bistable device illustrating the method of the invention;

FIG. 2 is a schematic sectional view of device;

FIG. 3 is a schematic sectional view oftwointerconnected bistable devices; and I i FIGS. 4 and 5 are schematic sectional views of fluidic registers.

In the arrangement of FIG. 7, the fluid supply port SP is opposite a splitter S of narrow angle, by means of which the issuing fluid can be guided into two different streams. If the pressure at the supply port is gradually increased from zero, the flow may initially be regarded as laminar and wall attachment will not occur, and as a result the fluid will flow substantially a biased bistable equally through the two outlets as divided by the splitters.

which was effective at a much lower pressure. In order to obtain maximum sensitivity the control signal must be applied before wall attachment takes place. I Y

For this effect to be readily exploited in practice, use is preferably made of an'oscillating supply which during each cycle, has its pressure reduced to below the critical value at which wall attachment first occurs and then increased to the necessary power level for the required operation of the device.

FIG. 2 shows a bistable device of the kind illustrated in FIG. I but having one of the sidewalls 11 disposed nearer to the axis of the supply port 12,- than the other sidewall 13. Consequently, the device is biased so that, inthe absence of a control signal, the jet adheres to the wall 11 and isthus directed into the adjacent outlet port 14. This device may be used as a latching gate. Consider the output at the output port 14 adjacent to the sidewall 11. If fluid is supplied to the supply port 12 prior to the application of a control signal to the control port 15 adjacent to the sidewall llthe jetwill adhere to the sidewall 11 and an output signal will persist while the supply to the port 12 is maintained and will not beaffected by subsequent application of a low pressure control signal to either of the control ports 15 and 16. v

On the other hand, if alow pressure control signal is applied to the control port 15 prior to the supply of fluid to the supply port 12 and is maintained during the formation of the jet, the latter will adhere to the'opposite sidewall 13 and no output will be received at the output port 14.- Thiscondition will continue for the duration of the supply of fluid to the supply port 12 independently of the control signal at the control port 15 and will be unaffected by subsequent low pressure signals at the other control port 16. Consequently the output at the port 14 is a 'latching INHIBIT function. i r

Consider now the output at the other output port 17. If no control signal is applied to the port 15 prior to the supply of fluid to the supply port 12, the jet will adhere to the sidewall 11 and no output signal will be received at the port l7. lhe subsequent application of a low pressure signal to either control port will not affect this output port 17. On the other hand, if a low pressure control signal is appliedto the control port 15 prior to the supply of fluid to the supply port'12, the jet will adhere to the sidewall 13 and an output signal will be received Y is a latching AND function.

jet greatly increases lowering the pressure in; the central part thereof. Under these conditions, the jet is in unstable equilibrium and in the absence of any specific control. it will attach itself due to some fortuitous lack of symmetry to one or other of v to the other. Once the issuing jet has been'set to one wall, the

supply pressure and flow can be increased considerably without producing any change and, moreover, without the possibility of change being produced by the-control pulse It will be realized that the application-of a low pressure control signal to the port 16 prior-to supply of fluid to the supply port 12 will merely reinforce the bias of the device. In fact connection of a permanent signal to thisport is an alternative method of biasing a device of this kind.

- Devices of this kind can also be biased by inclining the sup port port towards one sidewall. Alternatively one control port may be made larger than the other. This biases the jet towards the wall containing the smaller port. Further, one sidewall may be made longer than the other. This biasesthe jet towards the longer sidewall.

FIG. 3 shows an example of the invention applied to a bistable device with changeover by a trigger signal of a low power. The trigger stage shown on the left of the figure is fed from an oscillating supply by way of nozzle 21 and has oppositely located trigger control ports 23 and 24. It will be assumed that the oscillating supply falls below the critical wall attachment value during the reduced pressure phase. Consequently at the lowest value the issuing jet will be laminar and not attached to either walls 22 or wall 27. As shown, the system is biased in favour of sidewall 22, since this wall is closer to the centre of the nozzle 21 to which the oscillating supply is connected. As

-aresult of this condition, when the pressure rises above the critical value, the jet attaches itself to wall 22. Thus the oscil-- rises to-the value neededfor wall attachment, the flow at-- taches itself to sidewall 27'. As a result the oscillating supply is applied to port 28 and serves to switch the supply to the upper outlet along wall 29. 'The device will return to its previous I state yvhen the control signal is removed from port 24. If howeyei the reduced pressure of the oscillating supply does not I i fall below the wall attachment value, the transfer to wall 17 'll' ersist after the removal of the control signal applied to trol may have a monostable or a bistable-effect. The provision of the oscillating supply may be effected in known manner by means of a pure fluid oscillator why an oscillator employing moving p n Y 5 Referring to FIG."4, a stage of ajshift register comprises a and the memoryM eachcompri'ses a bistable deviceof the kind shown in FlGr'l, the'output ports 34 and 35 of the shift gate G being connected to the'contr'ol ports 36 and 37 of the memory M respectively. The outputports 40 and 42 of the .memory M provide 'read O'and 'readl" outputs respectively.

further details of the construction of the devicewill be apparent from the following descriptionof a typical sequence of operations. 1 A shift or strobe pulse is applied to the supply port.S of the shift gate G in the form of a pressure increasing fairly quickly from zero to its maximum value while a continuous pressure,-

which may be the same as this maximum value, is applied to the supplyport P- of the memory device at M. A small positive Iljow-level signal is applied to eitherthe'co'ntrol port 31 of thecontrol port 32 corresponding respectivelyto a and 1 value :which his desired to write into. the register.

' Consider the case in which it is desired to write 0. In this case, a suitable control signal is applied to port31 and when 4 andhencethere will be no flow by way of port 25 to ,sw ch 'th'e's'upply back to the lower outlet. Thus an extremely small-pressure and flow in control port 24 will reliably trigger a normally operated bistable wall attachment device, and de- 7 pendent on the range of the pressure variations cycle the conshift gate G and a memory orstore-Mk The figure also shows the shift G1 of the next stage of the register The shift gate G the shift signal is subsequently-applied to the supply port 5, the

.jet issuing from nozzle33 will attach itself to sidewall 34 and :lthus provide pressure to control port 36 to the memory device M.-=This sets the supply jet issuing from nozzle 38 to side wall 3 9 and gives a ,'read 0' output by way of the po rt 40. Similarly, if it had beendesired to write- I, the control pressure would have been applied to port 32 and would cause the jet from port33' to attach'to sidewall 35, thereby delivering the pres- ,sure to control port 37 to cause the supply jet from port 38 to attach to side wall 41 and thus provide a 'read 1 output by vway of port 42.

As mentioned. earlier, the control pressure, which is very ,small, suffices to determine the wall to which the'issuing jet shall becomeattached at a time whenthe'supply pressure is control ports 31 and 32. When. the shift signal attains its maxwhereby av component in a fluid logic system produces an am- .imum pressure, it produces a signal of sufficient magnitude at I one or other of control ports 36 and 37'to switch the memory device M if this is required. When the shift signal is at its maxirnum, it cannot be affected by any changein the signal at con- "trol ports 3l and 32 v In order to obtain from the outputs of the memory device a signal, the'level of which is sufficiently low not to detach a jet alreadyattached to a wall. so as to give suitable control signals for the shift gate G1 of the next stage, the output is restricted before connection to the control ports of the next stage. In FIG. 4 this is indicated by-a constriction 45, 46 in the flow passage but other means may be used for introducing high resistance to flow in the ports 43 and 44of the gate G9, for instance by making them narrower and/or longer. A further possibility is to move the control nozzle downstream of the shift pulse nozzle. This is shown for oneof the control ports at 58 in the arrangement of FIG. 5 which';will be described in due course. This displacement of thefcontrol port increases the pressure and flow required at the control port to detach a jet already attached to a wall but does notgreatly affect its action indetermining the-particular side wall to which the jet attaches on, reaching thecondition for attachment.

The'arrangement of FIG; 5 uses a biased device of the kind shown in FIG. 2, for the shift gate G. As before a symmetrical device is used for the memory. The biased device is given its monostable characteristic by taking sidewall 51 closer to the centre line, of nozzle 52 than sidewall 53-. Only one control input by way of port 55 is used to write in information which may be considered as representing-a1. Similarly only one output is required to provide the necessary write out and to control the succeeding stage. In the absence ofa'signal at the control port 55, the jet issuing from nozzle 52 when the shift pulse is applied attaches to sidewall 51, and when the full pressure of the pulse is developed, it is effective at nozzle 56 to switch the-supply jet to give a 'read 0 output at the output port 58 of thememory. In the presence of a signal at port 55 corresponding to a write 1 input,-when the shift pulse becomes effective the signal will cause the jet to attachto sidewall 53. Hence pressure is developed at the port 57 of the'memory and thus the bistable memory device will be reset so that the supply from port Pis delivered to nozzle 59 which is connected to the next stage. As already mentioned this is less effective in this position because his displaced somewhat from the jet,

produced by the shift pulse. The arrangement of FIG. 5 has I the advantagethat the read output 58 may be loaded quite considerably without affecting theoperation of the system.

The invention thus provides both a simple arrangement plification effect and-a latching fluidic device.

I claim: I

1. A method of controlling the flow of fluid in a wall at-. tachment device by applying low pressure fluid control signals to the control ports thereof, comprising directing fluid toward the inlet ends of a pair of mutually exclusive mechanically separated flow paths, applying a low pressure. fluid control signal to a said control portwhen the rate of flow of fluid toward said inlet ends is not greater than that at which wall attachment takes place,- increasing said flow rate until wall attachment has-occurred to a wall bounding one of said flow paths, maintaining said low pressure signal until said attachment has occurred-oscillatingthe rate of flow of fluid in the device between a maximum rate greater and a minimum rate less than, that. at which wall attachment first takes place, applying the outputsrof the devicerespectively to the control ports of a second bistable device through which fluid is flow-f.

ing at a rate which is greater than that at which wall at--- tachment takes place, and directing the flow of fluid more closely adjacent a wall of one said path than adjacent a wall of the other said path sothat in theabsence of a control signal the fluid attaches to said wall of said one path, whereby theoutput of the dvicealo'nglsaid one path is a latching'lNHlBlT function and the outputfrom the otherp'ath is-a latching AND 1 function. 

